Sheet steel is used extensively to form panels. The required structural characteristics, such as stiffness, vary depending upon the specific application. When higher stiffness values are required, the steel thickness is typically increased. Increasing sheet steel thickness, however, produces a panel which is not only heavier, but also more expensive.
A number of approaches have been taken in the past to provide improved structural characteristics of panels, without substantially increasing weight or materials cost. For example, composites of steel sheets having a solid polymer core have been used in applications where sound deadening and vibration dampers are required.
In U.S. Pat. No. 5,985,457, entitled STRUCTURAL PANEL WITH KRAFT PAPER CORE BETWEEN METAL SKINS, the entire disclosure of which is incorporated herein by reference, structural panels are disclosed which are laminate structures having metals skins separated by and bonded to an intervening layer of paper. The laminates described therein have high specific stiffness.
In U.S. Pat. No. 6,171,705, entitled “IMPROVED STRUCTURAL PANEL AND METHOD OF MANUFACTURE,” the entire disclosure of which is incorporated herewith, various techniques for fabricating laminates of steel and paper are described. The present invention provides several improvements to the method of simultaneously laminating and forming the composite laminates to produce shaped articles.